A heat barrier or insulator may be defined as any material which will impede the transfer of heat with reasonable effectiveness under normal conditions. Obviously, there are many processes and applications where elevated temperatures are either required or generated. When high temperatures are required, a substantial amount of energy is needed to produce the desired temperatures; a portion of this energy is lost from the process as heat escaping to the surrounding media. This energy loss may be reduced by successfully reducing the amount of heat escaping or by reducing the rate of escape. Doing so may provide for more efficient use of energy and reduce heat consumption levels.
Further, when high temperatures are generated within a device or apparatus and heat escapes, the environment in surrounding areas often are very uncomfortable. Excessive heat can be both a health risk and a deterrent to household and employee efficiency. Efforts to control hot environments often require large amounts of energy for cooling systems and fans. Thus, if such excess heat could be blocked, living and working conditions may be improved, and energy consumption may decrease.
Elevated temperature stability of non-woven fabrics is often associated with flame resistance and/or heat resistance). Thermal properties of materials have been studied for many years, and much of the existing work has been associated with the development and properties of heat resistant fibers such as Kevlar, Nomex, Novolid, PBI (polybenzimidazole), carbon, glass, ceramic, or other fibers. These fibers can be processed into woven fabrics or otherwise manufactured into non-wovennon-woven fabrics or blankets, which are then used in high heat environments to thermally insulate desired areas. Exemplary applications for heat-resistant fabrics include (a) fire blocking materials in aircraft, coach and train seats, (b) heat-resistant gloves, (c) slip sheets for roofs and decks, (d) fire-resistant linings and insulative padding in the automobiles, aircraft, and aerospace vehicles, and (e) furnace linings.
Because of the nature of the environments in which these materials are typically used, performance factors such as weight, thickness, volume, thermal conductivity, and expense can often limit the use of the materials. In addition, some of these materials can be hazardous in certain environments, and, as such, they must be covered (typically with a coating or the like) in order to be used.
In addition to the shortcomings set forth above, non-woven fabrics, such as those formed of glass or ceramic fibers, may raise additional issues. For example, such fabrics are typically formed in a one-step melt blowing process, in which a stream of short “staple” fibers is propelled onto a collector screen. The resulting product is typically non-uniform in thickness and fiber distribution, with the result that a relatively thick sample of material may be required in order to ensure desired thermal conductivity. Also, multi-filament glass fibers or filament yarns are typically extruded and cut into bundles of staple fibers. These are are relatively brittle; as a result, they are difficult to “card” (i.e., separate from each other), as breakage is high, as is jamming of the fibers due to static electricity (even when the fibers are sprayed with an antistatic liquid). Moreover, some of these materials are bonded with compositions that emit toxic fumes, particularly at high temperatures.
In view of the foregoing, it would be desirable to provide a thermally insulative material that can improve one or more of the listed performance factors and/or address one or more of the listed shortcomings of insulative non-woven fabrics.